Li_(2)O烧结助剂对固体氧化物燃料电池LSGM电解质烧结特性及离子电导率的影响

Effect of Li_(2)O Sintering Aid on Sintering Characteristics and Electrical Conductivity of LSGM Electrolyte for Solid Oxide Fuel Cell

本工作研究了Li_(2)O作为烧结助剂对固体氧化物燃料电池La_(0.8)Sr_(0.2)Ga_(0.8)Mg_(0.2)O_(3-δ)(LSGM)电解质烧结行为的影响规律,系统表征了烧结助剂含量和烧结温度对LSGM烧结体的致密度、微观组织结构、相组成以及离子电导率的影响。研究结果表明,Li_(2)O烧结助剂不仅可显著降低LSGM电解质的完全致密化烧结温度,还可以消除电解质粉体中原有的LaSrGa_(3)O_(7)杂相,并且抑制常规烧结过程中易于产生的MgO杂相,从而获得较高离子电导率的LSGM块体。当Li元素添加量为摩尔分数1%时,在1400℃烧结4 h获得的LSGM烧结体,其体密度达到理论密度的99%且为单一的钙钛矿结构。烧结体的离子电导率在800℃测试温度下达到最大值0.17 S/cm,相比未添加烧结助剂的试样提升20%以上。上述结果表明,通过添加适量的Li_(2)O作为烧结助剂对制备用于中温固体氧化物燃料电池(IT-SOFCs)高离子电导率的电解质具有重要意义。

This work investigated the influence of Li_(2)O as a sintering aid on the sintering behavior of La_(0.8)Sr_(0.2)Ga_(0.8)Mg_(0.2)O_(3-δ)(LSGM)electrolytes in solid oxide fuel cells,which systematically presented the effects of sintering aid content and sintering temperature on the density,microstructure,phase composition,and the ionic conductivity of sintered LSGM bulk.The results show that addition of Li_(2)O sintering aid not only reduces the sintering temperature,but also eliminates the LaSrGa_(3)O_(7) impurity phase in the sintered LSGM and suppresses the formation of MgO impurity phase which is easily generated during the conventional sintering process.Moreover,the addition of Li_(2)O increases the ionic conductivity of sintered LSGM electrolytes.When 1%(molar percentage)Li_(2)O is added,the LSGM bulk sintered at 1400℃ for 4 h reaches 99% of the theoretical density and presents a single perovskite structure.When tested at 800℃,the ionic conductivity of the sintered bulk reaches 0.17 S/cm,which is 20% higher than that of the sample without sintering aid.All results demonstrate that adding an appropriate amount of Li_(2)O as sintering aid is of great significance for the application of high ionic conductivity electrolyte in intermediatetemperature solid oxide fuel cells(IT-SOFCs).